Widespread Twilight Zone Detected Around Clouds | |
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killdamon (OP) User ID: 229344 United States 05/07/2007 07:04 PM Report Abusive Post Report Copyright Violation | Aerosols are tiny particles suspended in the air. Some occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels and the alteration of natural surface cover, also generate aerosols. Averaged over the globe, aerosols made by human activities currently account for about 10 percent of the total amount of aerosols in our atmosphere. Most of that 10 percent is concentrated in the Northern Hemisphere, especially downwind of industrial sites, slash-and-burn agricultural regions, and overgrazed grasslands. Scientists have much to learn about the way aerosols affect regional and global climate. We have yet to accurately quantify the relative impacts on climate of natural aerosols and those of human origin. Moreover, we do not know in what regions of the planet the amount of atmospheric aerosol is increasing, is diminishing, and is remaining roughly constant. Overall, we are even unsure whether aerosols are warming or cooling our planet. Aerosols & Climate Change Why do we care about aerosols? Scientifc studies of aerosols Related Articles: Changing Our Weather One Smokestack at a Time The effect of pollution on clouds and rainfall. Every Cloud has a Filthy Lining How the aerosols created by ship exhaust changes the structure of clouds. Figure 1. Aerosol particles larger than about 1 micrometer in size are produced by windblown dust and sea salt from sea spray and bursting bubbles. Aerosols smaller than 1 micrometer are mostly formed by condensation processes such as conversion of sulfur dioxide (SO2) gas (released from volcanic eruptions) to sulfate particles and by formation of soot and smoke during burning processes. After formation, the aerosols are mixed and transported by atmospheric motions and are primarily removed by cloud and precipitation processes. Why do we care about aerosols? Aerosols tend to cause cooling of the Earth's surface immediately below them. Because most aerosols reflect sunlight back into space, they have a "direct" cooling effect by reducing the amount of solar radiation that reaches the surface. The magnitude of this cooling effect depends on the size and composition of the aerosol particles, as well as the reflective properties of the underlying surface. It is thought that aerosol cooling may partially offset expected global warming that is attributed to increases in the amount of carbon dioxide from human activity. Figure 2a. (left) Clouds with low aerosol concentration and a few large droplets do not scatter light well, and allow much of the Sun's light to pass through and reach the surface. Figure 2b. (right) The high aerosol concentrations in these clouds provide the nucleation points necessary for the formation of many small liquid water droplets. Up to 90% of visible radiation (light) is reflected back to space by such clouds without reaching Earth's surface. Aerosols are also believed to have an "indirect" effect on climate by changing properties of clouds. Indeed, if there were no aerosols in the atmosphere, there would be no clouds. It is very difficult to form clouds without small aerosol particles acting as "seeds" to start the formation of cloud droplets. As aerosol concentration increases within a cloud, the water in the cloud gets spread over many more particles, each of which is correspondingly smaller. Smaller particles fall more slowly in the atmosphere and decrease the amount of rainfall. In this way, changing aerosols in the atmosphere can change the frequency of cloud occurence, cloud thickness, and rainfall amounts. If there are more aerosols, scientists expect more cloud drops to form. Since the total amount of condensed water in the cloud is not expected to change much, the average drop must become smaller. This has two consequences -- clouds with smaller drops reflect more sunlight (as explained in Figure 2a & b), and such clouds last longer, because it takes more time for small drops to coalesce into drops that are large enough to fall to the ground. Both effects increase the amount of sunlight that is reflected to space without reaching the surface. [link to earthobservatory.nasa.gov] Just passing thru. OG id 126286 NasTraDooMis |
Anonymous Coward User ID: 7883 United States 05/07/2007 07:04 PM Report Abusive Post Report Copyright Violation | |
NOx User ID: 233491 Serbia 05/07/2007 07:18 PM Report Abusive Post Report Copyright Violation | Aerosols (aero/air solids or particulates/fine particles) come from volcanic eruptions, winds including tornadoes and cyclones, areal pollution (industry of all sorts, our chimneys and motor vehicles), aircraft and many other things. This thread is a delibrate attempt to promote balamoot or the socalled "chemtrails". Doofus maximus... erm killdamon... grow up will you :) :danger_gas: |
Anonymous Coward User ID: 233521 United States 05/07/2007 08:02 PM Report Abusive Post Report Copyright Violation | This thread is a delibrate attempt to promote balamoot or the socalled "chemtrails". Quoting: NOxYes, you are partially correct. Chem/con trail formation is based upon aerosol particles acting as nucleated centers causing clouds and chem/con trails to form. It is not just the addition of water vapors to the atmosphere that causes trails. The word contrail, ie. condensation trail is itself a "con". |
killdamon (OP) User ID: 229344 United States 05/07/2007 08:09 PM Report Abusive Post Report Copyright Violation | This thread is a delibrate attempt to promote balamoot or the socalled "chemtrails". Quoting: Anonymous Coward 233521Yes, you are partially correct. Chem/con trail formation is based upon aerosol particles acting as nucleated centers causing clouds and chem/con trails to form. It is not just the addition of water vapors to the atmosphere that causes trails. The word contrail, ie. condensation trail is itself a "con". Just passing thru. OG id 126286 NasTraDooMis |
NOx User ID: 233666 Serbia 05/08/2007 08:18 AM Report Abusive Post Report Copyright Violation | Yes, you are partially correct. Chem/con trail formation is based upon aerosol particles acting as nucleated centers causing clouds and chem/con trails to form. It is not just the addition of water vapors to the atmosphere that causes trails. The word contrail, ie. condensation trail is itself a "con". Quoting: Anonymous Coward 233521Hm. Am I? Which part? So are you and you are also bias :) Ok. Here goes. Contrails/condensation trails are artificial cirriform clouds made by the exhaust of aircraft engines or wingtip vortices which precipitate a stream of tiny ice crystals in moist, freezing upper tropospheric air. They are sometimes beautiful to behold :) An airplane's engine exhaust increases the amount of moisture in the air, which can push the water content of the upper tropospheric air past the saturation point. This causes condensation to occur, and the contrail to form. In the upper troposhere this water vapour emerges into a usualy cold environment and the local increase in water vapour density condenses into tiny water droplets and/or desublimates into ice. At high altitudes, supercooled water vapour requires a trigger to encourage desublimation. The exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to rapidly turn to ice crystals. The aerosols/particulates that come from aircraft engine exausts are soot particles which are in fact the ones that act as the trigger for this desublimation which is logical is it not? |